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\(=\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{2021}-\dfrac{1}{2024}=\dfrac{1}{4}-\dfrac{1}{2024}=\dfrac{505}{2024}\)
\(\dfrac{3}{4.7}+\dfrac{3}{7.10}+\dfrac{3}{10.13}+...+\dfrac{1}{2021.2024}\)
=\(\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{14}+...+\dfrac{1}{2021}-\)\(\dfrac{1}{2024}\)
=\(\dfrac{1}{4}-\dfrac{1}{2024}\)
=\(\dfrac{505}{2024}\)
B = \(\frac{2^{10}.13+2^{10}.65}{2^8.104}=\frac{2^{10}.\left(13+65\right)}{2^8.104}=\frac{2^{10}.78}{2^8.104}\)
B = \(\frac{2^2.39}{52}=\frac{2^2.39}{2^2.13}\)
B = \(\frac{39}{13}\)
B = 3
B = \(\frac{2^{10}.13-2^{10}.65}{2^8.104}=\frac{2^{10}.\left(13+65\right)}{2^{8.104}}=\frac{2^{10}.78}{2^8.104}=\frac{2^2.39}{52}=\frac{2^2.39}{2^2.13}=\frac{39}{13}=3\)
\(\frac{2^{10}.13+2^{10}.65}{28.104}\)=\(\frac{2^{10}.13+2^{10}.5.13}{2^2.7.2^3.13}\)
=\(\frac{2^{10}.13.\left(5+1\right)}{2^2.7.2^3.13}\)
=\(\frac{2^{10}.13.6}{2^5.7.13}\)
=\(\frac{2^5.6}{7}\)
=\(\frac{32.6}{7}\)
=\(\frac{192}{7}\)
\(\frac{2^{10}.13+2^{10}.65}{2^8.104}=\frac{2^{10}.13+2^{10}.5.13}{2^8.2^3.13}=\frac{2^{10}.13\left(1+5\right)}{2^{11}.13}=\frac{2^{10}.13.2.3}{2^{11}.13}=\frac{2^{11}.3.13}{2^{11}.13}=3\)
A=6/4.7+6/7.10+6/10.13+...+6/73.76
\(=2.\left(\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+...+\frac{3}{73.76}\right)\)
\(=2.\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+...+\frac{1}{73}-\frac{1}{76}\right)\)
\(=2.\left(\frac{1}{4}-\frac{1}{76}\right)=2.\frac{9}{38}=\frac{9}{19}\)
\(=>C=\frac{3}{4}-\frac{3}{7}+\frac{3}{7}-\frac{3}{10}+....+\frac{3}{73}-\frac{3}{76}\)
\(=>C=\frac{3}{4}-\frac{3}{76}\)
\(=>C=\frac{54}{76}\)
\(=>C=\frac{27}{38}\)
\(C=\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+....+\frac{3}{73.76}\)
=> Cộng vế với vế , ta được :
\(C=\frac{3}{3}\left(\frac{1}{4.7}+\frac{1}{7.10}+\frac{1}{10.13}+....+\frac{1}{73.76}\right)\)
\(\Rightarrow C=1\left(\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+....+\frac{1}{73}-\frac{1}{76}\right)\)
\(\Rightarrow C=1\left(\frac{1}{4}-\frac{1}{76}\right)\)
\(\Rightarrow C=1\left(\frac{19}{76}-\frac{1}{76}\right)=1\frac{18}{76}\)
a: \(A=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{201}-\dfrac{1}{203}=\dfrac{1}{3}-\dfrac{1}{203}=\dfrac{200}{609}\)
b: \(B=\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{73}-\dfrac{1}{76}\)
\(=\dfrac{1}{4}-\dfrac{1}{76}=\dfrac{18}{76}=\dfrac{9}{38}\)
Trả lời
25.125.4.8=(25.4)(125.8)=100.1000
=100000
10.25+10.13+38.90
=10(25+13)+38.90
=38.10+38.90
=38(90+10)
=38.100=3800
Hok tốt k nha
=100000
=3800
hk tốt